As is known, a trocar is generally made of a stylet having a sharp tip for penetrating through an abdominal wall and surrounding tube through which gas or the like may be injected or exhausted from the abdomen after puncturing by the stylet. Further, in order to protect a patient or surgeon from injury through inadvertent contact with the sharp tip, protective tubes have been positioned over the stylet tip, for example, as described in U.S. Pat. No. 4,601,710. In this case, the stylet is secured to a housing with a spring-biased protective tube concentrically about the stylet. When put to use, the protective tube is able to move proximally to expose the sharp tip for penetrating the abdominal wall without interference. Once a puncture has been made, the protective tube is able to slide distally under the force of the spring to again cover over the sharp tip to preclude injury to tissue within the abdomen. Thereafter, the stylet can be removed from the abdomen.
In addition, the known trocar has been constructed so that the housing secured to the stylet can be fitted into and rotated relative to a second housing containing an outer tube through which the stylet and protective tube may pass. Further, the second housing has had a flap valve which cooperates with a groove in the protective tube in order to lock the spring-biased protective tube in an extended position over the sharp stylet tip. Generally, the trocar is delivered for use in this locked condition so as to protect the user from being injured by the sharp tip of the stylet. However, prior to use, the housing connected to the stylet must be pushed into an unlocked position so that the protective tube can retract from the sharp tip in order to puncture an abdominal wall.
In the event that the trocar is not delivered in the locked position, there is a risk that users may be damaged should the protective tube inadvertently be retracted to expose the sharp stylet tip. Further, any exposed tissue of a patient may be damaged should the protective tube be retracted inadvertently prior to proper positioning of the stylet for penetrating an abdominal wall.
Accordingly, it is an object of the invention to provide a trocar in which the risk of injury due to inadvertant retraction of a protective tube over a sharp stylet tip can be significantly reduced.
It is another object of the invention to shield the sharp tip of a stylet of a trocar in a positive manner at all times prior to actual use.
It is another object to the invention to provide a relatively simple structure for shielding the sharp tip of a trocar until ready for use.
It is another object to the invention to provide a relatively simple mechanism for unlocking a trocar for use.